Questions on Lapping?

[KennyH]

I just lapped my celeron 300A to full copper and now it is stable at 504. I just wanted to know how can you tell that you are getting close to the silicon bed underneath the copper? I would really like to know so that I want kill it. Any help would be greatly appreciated. Thanks.

 

[Wingznut]

Once you get to all copper, there's no point in going any further.